1. Field of the Invention
A freewheel drive for the starter of an internal combustion engine. This invention relates to a freewheel drive for the starter of an internal combustion engine, with ring members arranged coaxially to one another, and with roller bodies disposed between a circular peripheral surface of the first ring member and a peripheral surface of the second ring member which has cam tracks extending eccentrically of the axis. Each roller body is biased by an associated spring into a clamping position which permits relative movement of the ring members in one rotary direction only. The freewheel drive also comprises a driving pinion connected to one of the ring members, and a sleeve connected to the other ring member for the reception of a drive shaft.
2. Description of the Related Art
Known freewheel drives of this type have long been used as a part of the starter, especially for starting a mechanically propelled vehicle. In them, the sleeve which embraces the starter drive shaft is moved axially by means of a clutch relay, so that the driving pinion, located at the end of the freewheel drive remote from the sleeve, engages with the starter ring gear of the internal combustion engine. As soon as the internal combustion engine is caused to start, the driving pinion, having its teeth still engaged, must be able to carry forward with respect to the starter shaft, until the toothed engagement between the driving pinion and the ring gear of the engine is neutralised, for which reason this connection between the starter shaft and the engine ring gear is designed as a freewheel.
The freewheels used for this purpose always have roller bodies between a circular peripheral surface of a ring member and a peripheral surface of a further ring member having cam tracks extending eccentrically of the axis, which roller bodies act as clamps in one rotary direction of one or the other ring member, so that one ring member carries the other with it, while in the opposite direction of rotation, as a result of the freewheel effect which then arises, relative rotation of the ring members is possible. The actual direction of rotation can be right or left according to the design of the starter.
In a freewheel of this type the roller bodies consist of rollers, each biased into the clamping position by a respective spring. The springs must be held, and the plurality of springs and rollers must be mounted in the most practical manner, for which reason annular carriers with support elements for the springs have been designed in the most various forms.
Of the two ring members concentric to one another, the one whose peripheral surface has the cam tracks extending eccentrically of its axis was previously manufactured by milling with removal of swarf, and the outer ring member was always chosen, its inner peripheral surface being milled, until the time arrived when these members were manufactured by pressing or some other rational process. This outer ring member, in the freewheels of the above-described type, is integrally connected by means of a flange with the sleeve which serves for reception of the starter shaft. The component of one-piece design made in this way forms a housing for the reception of the inner ring member.
This housing with its inner peripheral surface having cam tracks extending eccentrically of the axis is also manufactured in the same manner as described above. The inner ring member with its integrally united driving pinion is likewise manufactured by cold flow pressing. As a variant on this kind of design, of course, the driving pinion could also be connected to the outer ring member by way of a flange, and the inner ring member could be connected with the sleeve for receiving the shaft of the starter.
The known freewheel drives of the above-described type sometimes fail when overloaded or when the ambient temperature is very low. In these cases the roller bodies no longer maintain the clamping action on the circular peripheral surface of the inner ring member, and thus the drive is ineffective. This disadvantage has the consequence that a powered vehicle equipped with this freewheel drive must be pushed or towed, unless in exceptional cases a starting handle is provided for starting the engine. The wear which arises is then a further disadvantage, or there is a total failure to function. A disadvantage in the known freewheel drives is that the manufacture of the profiled peripheral surface of the outer ring member with its axially eccentrically disposed cam tracks is costly from the tooling aspect, if one considers the less expensive possibility of machining the cam tracks into the inner ring member with its smaller diameter. Finally, in the known freewheel drives, special additional constructional elements are also provided, for effecting a lubricant-tight seal of the annular space which encloses the roller bodies and the springs.